Power semiconductor with a Si chip and a wideband chip having matched loss and area ratios

ABSTRACT

A power semiconductor apparatus which is provided with a first power semiconductor device using Si as a base substance and a second power semiconductor device using a semiconductor having an energy bandgap wider than the energy bandgap of Si as a base substance, and includes a first insulated metal substrate on which the first power semiconductor device is mounted, a first heat dissipation metal base on which the first insulated metal substrate is mounted, a second insulated metal substrate on which the second power semiconductor device is mounted, and a second heat dissipation metal base on which the second insulated metal substrate is mounted.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 12/707,909 filed Feb. 18, 2010, now U.S. Pat. No. 8,441,075 issuedMay 14, 2013, which claims the foreign priority benefit under Title 35,United States Code, §119(a)-(d) of Japanese Patent Application No.2009-080850, filed on Mar. 30, 2009, the contents of which are herebyincorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a power semiconductor apparatus whichis provided with a power semiconductor device using Si as a basesubstance and a power semiconductor device using a wide-gapsemiconductor as a base substance.

DESCRIPTION OF RELEVANT ART

A wide-gap semiconductor device using silicon carbide (SiC) or galliumnitride (GaN) which has a wider energy bandgap than that of silicon (Si)is getting a lot of attention. Since these materials have a breakdownfield ten times higher than that of Si and thereby a drift layer forsecuring a breakdown voltage can be made thin about 1/10 in comparisonwith Si, a lowering of ON-voltage of a power semiconductor device andoperation thereof at high temperature can be achieved.

In such a power semiconductor apparatus as a semiconductor module whichis used as an inverter in the fields of railway, industries, automobile,home appliances or power sources, a switching device such as IGBT and arecirculation diode are connected in anti-parallel. When a powersemiconductor device using Si as a base substance and a powersemiconductor device using SiC or GaN as the base substance are mountedon the power semiconductor apparatus, a junction temperature (Tj) of thepower semiconductor device using Si is limited to not more than 175° C.On the other hand, the power semiconductor device using SiC or GaN asthe base substance can operate even if the junction temperature (Tj)) isnot less than 200° C. Therefore, as described in JP2004-47883, a powersemiconductor apparatus which sandwiches a heat insulator between apower semiconductor device using Si as the base substance and a powersemiconductor device using SiC or GaN as the base substance has beenproposed.

In addition, a leakage current of the power semiconductor device usingSiC or GaN as the base substance is large due to the effect of crystaldefects. Especially, a leakage current of a Schottky-barrier diode usingSiC or GaN becomes large.

In the power semiconductor apparatus described in JP2004-47883, thepower semiconductor device using Si as the base substance and the powersemiconductor device using SiC or GaN as the base substance are bothmounted on a collector electrode. In this case, a heat generated in thepower semiconductor device using SiC or GaN as the base substance islikely to be transferred to a mounting portion of the powersemiconductor device using Si as the base substance via the collectorelectrode.

In addition, a voltage terminal on the side of the positive electrode(collector) and a voltage terminal on the side of the negative electrode(emitter) of the module, on which the power semiconductor device usingSi as the base substance and the power semiconductor device using SiC orGaN as the base substance are mounted, are commonly-formed for thedevices, and when a leakage current between the terminals of thepositive terminal and the negative terminal is measured, a leakagecurrent of the power semiconductor device using SiC or GaN as the basesubstance becomes larger than that of the power semiconductor deviceusing Si as the base substance. Therefore, it is difficult to accuratelymeasure leakage current characteristics of the power semiconductordevice using Si as the base substance.

The present invention has been developed in consideration of theforegoing problems, and it is an object of the present invention toprovide a power semiconductor apparatus which is thermally andelectrically highly reliable even if a power semiconductor device usingSi as the base substance and a power semiconductor device using SiC orGaN as the base substance are mounted in mixture (mixedly) on the powersemiconductor apparatus.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda power semiconductor apparatus which is provided with a first insulatedmetal substrate on which a first power semiconductor device using Si asa base substance is mounted, a first heat dissipation metal base onwhich the first insulated metal substrate is mounted, a second insulatedmetal substrate on which a second power semiconductor device using asemiconductor having an energy bandgap wider than the energy bandgap ofSi as a base substance is mounted, and a second heat dissipation metalbase on which the second insulated metal substrate is mounted.

In addition, according to a second aspect of the present invention,there is provided a power semiconductor apparatus, where a positive anda negative main terminals to which the first power semiconductor deviceusing Si as the base substance are connected, and a positive and anegative main terminals of the second power semiconductor device using asemiconductor having an energy bandgap wider than the energy bandgap ofSi as a base substance are connected are electrically separated.

Here, it is preferable that the first power semiconductor device is aswitching device such as an IGBT and the second power semiconductordevice is a diode such as a Schottky-barrier diode. In addition, as asemiconductor having an energy bandgap wider than the energy bandgap ofSi, SiC, GaN and diamond may be used.

Since a power semiconductor device using Si as a base substance and apower semiconductor device using a semiconductor having an energybandgap wider than the energy bandgap of Si are mounted on respectiveinsulated metal substrates, and in addition, since the insulated metalsubstrates are mounted on respective heat dissipation metal bases, aheat conduction between both the power semiconductor devices can besuppressed. Furthermore, since the positive and the negative mainterminals of the power semiconductor device using Si are electricallyseparated from those of the power semiconductor device using asemiconductor having an energy bandgap wider than the energy bandgap ofSi, leakage currents of both power semiconductor devices can beaccurately measured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a mounting arrangement of a power semiconductor apparatusaccording to a first embodiment of the present invention;

FIG. 2 is a circuit diagram of a power semiconductor apparatus accordingto the first embodiment;

FIG. 3 is a mounting arrangement example of a conventional powersemiconductor apparatus;

FIG. 4 is a circuit diagram of a conventional power semiconductorapparatus;

FIG. 5 is a measurement example of a leakage current of a conventionalpower semiconductor apparatus;

FIG. 6 is a measurement example of a leakage current of the powersemiconductor apparatus according to the first embodiment;

FIG. 7 is a mounting arrangement of a power semiconductor apparatusaccording to a second embodiment of the present invention;

FIG. 8 is a mounting arrangement example of a conventional powersemiconductor apparatus;

FIG. 9 is a power loss when a power semiconductor apparatus according tothe embodiment of the present invention is applied to an inverter;

FIG. 10 is voltage and current waveforms when a SiC-SBD is applied to apower semiconductor apparatus; and

FIG. 11 is a mounting arrangement of a power semiconductor apparatusaccording to a third embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiments of the present invention will be described in detail byreferring to drawings.

FIG. 1 shows a mounting arrangement of a power semiconductor apparatusaccording to a first embodiment of the present invention. In theembodiment, IGBT 11 which is a switching device using Si as a basesubstance (hereinafter, referred to as Si-IGBT) is bonded to and mountedon an insulated metal substrate 32 by, for example, solder and aSchottky-barrier diode (hereinafter, referred to as SiC-SBD) 12 which isa diode using SiC as a base substance is bonded to and mounted onanother insulated metal substrate 31 by, for example, solder. Inaddition, the insulated metal substrate 32 on which the Si-IGBT 11 ismounted is bonded to a heat dissipation metal base 39 by solder and theinsulated metal substrate 31 on which the SIC-SED 12 is mounted isbonded to a heat dissipation metal base 38 by solder, and both theinsulated metal substrates 31, 32 are integrated by a resin case 40 as amodule. Here, the heat dissipation metal base 38 on which the insulatedmetal substrate 31 is mounted and the heat dissipation metal base 39 onwhich the insulated metal substrate 32 is mounted are arranged onsubstantially the same plane in the module, and apart of the resin case40 lies between the heat dissipation metal bases 38, 39. In addition,when a power semiconductor apparatus according to the embodiment isapplied to, for example, an inverter, the heat dissipation metal bases38, 39 are in contact with a surface of heat dissipation fin at backsides of mounting surfaces of the insulated metal substrates 31, 32. Acollector terminal 22, an emitter terminal 21, an emitter controlterminal 23 and a gate control terminal 24 are connected to theinsulated metal substrate 32 by, for example, solder bonding. Inaddition, a cathode terminal 25 and an anode terminal 26 are connectedto the insulated metal substrate 31 by, for example, solder bonding.

FIG. 3 shows a mounting arrangement example of a conventional powersemiconductor apparatus. In a mounting method of the conventional powersemiconductor apparatus, the Si-IGBT 11 and the SiC-SBD 12 are mountedon the same insulated metal substrate 31. In this case, due to a heatgeneration of the Si-IGBT 11 and the SiC-SBD 12, a heat is likely to betransferred to each of the chips via the insulated metal substrate 31.Therefore, although a SiC-SBD generally can operate at a highertemperature in comparison with a Si-IGBT, an operation temperature ofthe SiC-SBD 12 is limited to that of the Si-IGBT 11. On the other hand,in the first embodiment, since the heat dissipation metal base 39including the insulated metal substrate 32 on which the Si-IGBT 11 ismounted is separated from the heat dissipation metal base 38 includingthe insulated metal substrate 31 on which the SiC-SBD 12 is mounted, theSiC-SBD 12 can be operated at a high temperature without limitation ofthe operation temperature of the Si-IGBT 11.

FIG. 2 shows a circuit diagram of a power semiconductor apparatusaccording to the first embodiment. The collector terminal 22 and theemitter terminal 21 which are connected to the Si-IGBT 11 are separatedfrom the cathode terminal 25 and the anode terminal 26 which areconnected to the SiC-SBD 12. That is, in a power semiconductor apparatuswhich has no external wiring connection, a positive and a negative mainterminals of the Si-IGBT 11 are not connected to a positive and anegative main terminals of the SiC-SBD 12 by internal wiring, and thepositive and the negative main terminals of the Si-IGBT 11 areelectrically separated from the positive and the negative main terminalsof the SiC-SBD 12.

FIG. 4 shows a circuit diagram of the conventional power semiconductorapparatus in FIG. 3. In the conventional power semiconductor apparatus,a collector terminal of the Si-IGBT 11 and a cathode terminal of theSiC-SBD 12 are both connected to the collector terminal 22, and anemitter terminal of the Si-IGBT 11 and an anode terminal of the SiC-SBD12 are both connected to the emitter terminal 21. In the SiC-SBD 12, aleaking current (leakage current) of the SiC-SBD 12 at OFF-state isabout one digit larger than that of the Si-IGBT 11. Therefore, in theconventional power semiconductor apparatus, when a leakage currentbetween, the collector terminal and the emitter terminal is measured,only a leakage current mostly by the SiC-SBD is measured as shown inFIG. 5, thereby resulting in difficulty in measuring a leakage currentof the Si-IGBT. Accordingly, it is difficult to conduct an accurateinspection of the leakage current of the Si-IGBT 11 in the inspectionprocess of the module.

In contrast, in the embodiment of the present invention, as shown inFIG. 6, a leakage current of the Si-IGBT can be accurately measured byseparating a collector terminal of the Si-IGBT 11 from a cathodeterminal of the SiC-SBD 12 and an emitter terminal of the Si-IGBT 11from an anode terminal of the SiC-SBD 12. In addition, since thepositive and negative main terminals of the Si-IGBT 11 are separatedfrom the positive and negative main terminals of the SiC-SBD 12 withinthe power semiconductor apparatus and they are not connected to eachother by an internal conductor, that is, by a thermal conductor, athermal conduction between the main terminals of the Si-IGBT 11 and theSiC-SBD 12 can be prevented. Therefore, combined with use of individualinsulated metal substrates 31, 32 and individual heat dissipation metalbases 38, 39, the SIC-SBD 12 can be operated at a high temperaturewithout limitation of the operation temperature of the Si-IGBT 11.

In the embodiment, a distance between the Si-IGBT 11 and the SiC-SBD 12increases due to mounting of the Si-IGBT 11 and the SiC-SBD 12 on theindividual insulated metal bases, respectively. However, by disposing adifferent main terminal for each device, the connection between thedevices can be made with a low inductance wiring outside the module anda reverse recovery current (recovery current) of the SiC-SBD becomessmall. As a result, effect of a wiring inductance between the Si-IGBT 11and the SiC-SBD 12 can be reduced.

It is noted that if a collector terminal of the Si-IGBT 11 is separatedfrom a cathode terminal of the SiC-SBD 12, it is unnecessary to separatean emitter terminal of the Si-IGBT 11 from an anode terminal of theSiC-SBD 12 for accurately measuring a leakage current of the Si-IGBT 11.In addition, instead of the above, an emitter terminal of the Si-IGBT 11may be separated from an anode terminal of the SiC-SBD 12 for accuratelymeasuring a leakage current of the Si-IGBT 11.

In the embodiment, a power semiconductor device using Si as a basesubstance is an IGBT. However, a switching device, for example, aMOS-FET, a MIS-FET and a junction FET may be used. In addition, a powersemiconductor device using SiC as a base substance is a Schottky-barrierdiode. However, a PiN diode may be used. Furthermore, other than SiC, awide-gap semiconductor such as GaN may be used.

FIG. 7 shows a mounting arrangement of a power semiconductor apparatusaccording to a second embodiment of the present invention. The samecomponent and a terminal having the same function with the firstembodiment are shown with the same symbol.

FIG. 8 shows a mounting arrangement example of a conventional powersemiconductor apparatus. In the mounting arrangement example, fourSi-IGBT 11 and two SiC-SBD 12 are mounted on a single insulated metalsubstrate 32 and six insulated metal substrates 32 are mounted on theheat dissipation metal base 38 to form a power semiconductor module. Inthis case, due to heat generation of the Si-IGBT 11 and the SiC-SBD 12,a heat is likely to be transferred to each chip via the insulated metalsubstrate 32.

In contrast, in the embodiment of FIG. 7, four insulated metalsubstrates on each of which six Si-IGBT 11 are mounted are mounted onthe heat dissipation metal base 39 as with the first embodiment, andsimilarly, two insulated metal substrates 31 on each of which sixSiC-SBD 12 are mounted are mounted on the heat dissipation metal base 38to form a power semiconductor module. In the embodiment, as with thefirst embodiment, the heat dissipation metal base 39 including theinsulated metal substrate 32 on which the Si-IGBT 11 is mounted isseparated from the heat dissipation metal base 38 including theinsulated metal substrate 31 on which the SiC-SBD 12 is mounted.Accordingly, the SiC-SBD 12 can be operated at a temperature higher thanthe operation temperature of the Si-IGBT 11.

In addition, a collector terminal of the Si-IGBT 11 is separated from acathode terminal of the SiC-SBD 12 and an emitter terminal of theSi-IGBT 11 is separated from an anode terminal of the SiC-SBD 12.Therefore, as with the first embodiment, it becomes possible to measurea leakage current of the Si-IGBT 11 accurately.

FIG. 9 shows a power loss reduction effect when a power semiconductorapparatus according to the first or the second embodiment of the presentinvention is applied to an inverter, which is an electric powerconversion system. A calculation example of power loss of a conventionalinverter is shown on the left in FIG. 9. An inverter loss is mainlycaused in a switching device and a diode. A loss caused by the switchingdevice is expressed by a sum of a conduction loss, a turn-ON loss and aturn-OFF loss, and a loss caused by the diode is expressed by a sum of aconduction loss and a recovery loss. Meanwhile, in the conventionalinverter, a Si-IGBT and a PiN diode of Silicon (hereinafter, referred toas Si-PiN diode) are used. The ratio of a conduction loss to a switchingloss varies depending on a frequency of the inverter. However, the ratioof an IGBT loss to a diode loss is approximately 2:1 even if thefrequency of the inverter is varied. Therefore, if the ratio of an IGBTchip size to a diode chip size is set to 2:1, the ratio of a heatresistance of the chip to a heat resistance of the insulated metalsubstrate becomes 1:2. As a result, the junction temperatures of thechips can be set substantially the same.

As shown in FIG. 9, according to the embodiment of the presentinvention, the recovery loss and the turn-ON loss are mainly reduced,and a total loss of the inverter is substantially reduced in comparisonwith the conventional one.

FIG. 10 is voltage and current waveforms when a SiC-SBD is applied to apower semiconductor apparatus. If a Si-PiN diode is replaced by aSiC-SBD, a recovery loss of the diode becomes substantially 0 (zero),thereby can be reduced to about 1/10 as shown in an upper drawing inFIG. 10, and since the recovery current is not superimposed at theturn-ON, the turn-ON loss can be reduced to about ½.

In this case, since the diode loss can be reduced to about ½ incomparison with the conventional one, a chip size of the SiC-SBD can bereduced to about ¼ of that of the Si-IGBT. Therefore, in a powersemiconductor apparatus according to the embodiment of the presentinvention, the ratio of a device area of a power semiconductor deviceusing Si as a base substance to a device area of a power semiconductordevice using SiC or GaN as a base substance becomes 0.8 to 1.2 times theratio, e.g. the quotient, of a device loss of the power semiconductordevice using Si as a base substance to (divided by) a device loss of thepower semiconductor device using SiC or GaN as a base substance.

In the foregoing embodiment in FIG. 7, a chip size of SiC is reduced to¼ as described above. If a SIC-SEM, a SiC-PiN diode, a GaN-SBD, or aGaN-PiN is used, a device area of a power semiconductor device using SiCor GaN as a base substance can be reduced to not more than ⅓ of a devicearea of a power semiconductor device using Si as a base substance. As aresult, a size of the power semiconductor apparatus can be reduced,while ensuring the reliability.

FIG. 11 shows a mounting arrangement of a power semiconductor apparatusaccording to a third embodiment of the present invention. A size of thepower semiconductor apparatus was reduced by reducing a device area ofthe IGBT that is a power semiconductor device using Si as a basesubstance.

The embodiments of the present invention have been described in detail.However, the present invention is not limited to the foregoingembodiments, and it is obvious that various changes may be made withoutdeparting from the scope of the technical idea of the present invention.

What is claimed is:
 1. A power semiconductor apparatus comprising: afirst power semiconductor device using Si as a base substance; and asecond power semiconductor device using a semiconductor as a basesubstance which has an energy bandgap wider than an energy bandgap ofSi; and wherein a ratio of a device area of the first powersemiconductor device to a device area of the second power semiconductordevice is 0.8 to 1.2 times a ratio of a device loss of the first powersemiconductor device to a device loss of the second power semiconductordevice; and wherein the first power semiconductor device is an IGBT andthe second power semiconductor device is a Schottky-barrier diode.